Yfz Athena 480cc

[XCprorider123]

I heard Athena wasnt no good

[kb motorsports]

Originally Posted by XCprorider123

I heard Athena wasnt no good

You heard wrong either by communication problem or from some company who is trying to up sell a 900+ Cylinder kit.

ATV Performance Parts
270-774-1982

[Scottyamaha]

Yhup heard wrong indeed! I love mine. Never has once failed me. Thank you Athena!

[04yfz450bb]

Currently in the making 2004 athena 478ccBB, hotrods stock crank..was wondering what to do with the head...valves(bigger,stock,kibble white etc.) Polished and ported or just ported?

[pnut250]

know can you add an 3 mill stroker to this kit. i assume it would be if all clearences are right

[Terse]

Originally Posted by pnut250

know can you add an 3 mill stroker to this kit. i assume it would be if all clearences are right

Yes you can add a stroker to this Athena kit. Just check all clearances and make sure the stroker kit is not going to drop the piston so low into the cases to hit anything.

[pnut250]

ty terse

[dieselholic]

i keep reading about how these athena pistons are junk but nobody ever says why or what problems they have with them. some details would be nice. also im just ordered a big bore kit and im guessing you can still run the cam mod with the kit? correct me if im wrong

[dieselholic]

anyone?

[YFZ450~BENCE]

cam mod is fine. has nothing to do with how big am engine is. don't know on piston as I haven't run them. I hear its junk all the time too but haven't really heard of failures either

[Terse]

Originally Posted by dieselholic

i keep reading about how these athena pistons are junk but nobody ever says why or what problems they have with them. some details would be nice. also im just ordered a big bore kit and im guessing you can still run the cam mod with the kit? correct me if im wrong

Yes you can run the cam mod with this mod.

Athena pistons are very heavy compared to other same bore size pistons.

The dome/ dish shape of the piston top is not horrible.... but the piston at tdc is lower in the bore then stock and thus the squish band becomes horrible. The piston then becomes less compression then stock too. Which IMO is not the best idea.

The piston rings are heavy.

The wrist pin is heavy.

The wrist pin oil delivery set up royally sucks. The yfz already has poor wrist pin oiling, so why make it worse.

The piston has no anti det grooves, and other grooves that help keep rings seated.

BUT....... if some one is not looking for the "best" and is willing to settle for a cheap bolt on piston that will work.... it's OK.

[Terse]

Also, to clarify.....

"Junk" doesn't mean "failure". Just a sub par piston design.

A solid chunk of iron will never fail under normal situations.

A super heavy piston is not something that will rev out fast and high like the yfz is designed to do.

[dieselholic]

thank you Terse. that is exactly what i was looking for. i didnt know if the piston was going to come up higher than stock and the exhaust valves would have clearance. i just got the oil upgrade done so hopefully no problems with the wrist pin. one more question. if the compression ratio is less than stock with this big bore kit. do you know how much? enough that another piston is going to make a big difference?

[Terse]

Originally Posted by dieselholic

thank you Terse. that is exactly what i was looking for. i didnt know if the piston was going to come up higher than stock and the exhaust valves would have clearance. i just got the oil upgrade done so hopefully no problems with the wrist pin. one more question. if the compression ratio is less than stock with this big bore kit. do you know how much? enough that another piston is going to make a big difference?

I can not give ya the exact comp details with out spec-ing out the motor with the gaskets being used, but mine when I ran the stock Athena piston and gaskets was in the 11.4-11.7 range. I ran it for a trip or two to get a feel for it and dyno tune it, and it ran ok. However going with a better piston (Venom) and better gaskets there was a very noticeable gain in performance both on the dyno and while riding it.

I would not change out the Athena piston for another stock comp piston for compression reasons, but more for having a better piston in there.

[dieselholic]

alright. thanks again!!

[thumpers4life]

Would this also effect the 2004 and 2005 motors with the shorter stroke?

[Terse]

Originally Posted by thumpers4life

Would this also effect the 2004 and 2005 motors with the shorter stroke?

Yes it still applies. Yes, the 04/05 has a shorter stroke, but it also has a longer rod then the 06+ cranks. 04/05 rod length is not as long as the WR however.

So the whole point is this...

Dry fit parts to see where your at, and don't be surprised if you need to raise the jug. If you do, then you have an idea of what it will take, and if not..... cool.

[IGottaYFZ]

Where can I get a WR 98mm piston that will run pump gas? I have emailed the guys at kbr and have not heard a reply. Thought maybe they are on vacation?

[Terse]

Originally Posted by IGottaYFZ

Where can I get a WR 98mm piston that will run pump gas? I have emailed the guys at kbr and have not heard a reply. Thought maybe they are on vacation?

Try KBmotors.

Then CP.

Then mmad.

Then ebay.

[YFZ450~BENCE]

then craigslist